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Re: Soil Compaction in Pasture



Phil:  I would have made the same assumption, but for two points.  
First, the Aerway rotovator device (rotating cylinder with knives to 
slit open the soil) originated, I believe, in the UK or nearby, where 
stock are out and grazing on heavier, wetter soils, for longer times, 
than we might do.  Under those conditions, the Aerway or like devices 
seem to be necessary to overcome the compactive effect of livestock, 
or wheel traffic, or whatever.  

Secondly, we did a multi-year trial at a heavy, wettish (but tile 
drained), silty, clay loam, 10 ac site here at Guelph.  The study 
compared a) clipping vs. grazing by b) cattle or c) sheep.  Species 
persistence in mixture differed sharply between clipped and grazed 
conditions, so in trying to interpret why, one of the measurements 
was of soil fertility after 5 years of these treatments.  My 
technician broke several sampling units in sampling the cattle-grazed 
treatments, but had no difficulty getting samples in the clipped 
treatments.  Bred heifers and dry cows grazed these treatments most 
of the season, but were withdrawn when conditions were just too wet 
and pugging was a problem.  So, the kind of compaction we observed 
might be considered typical - not from mismanagement - for heavy, wet 
soils.

    Might add, however, that the sampling exercise was done at the 
end of the season.  Winter freeze/thaw activity might well have 
loosened this up considerably by the following spring, so I wouldn't 
want to overinterpret the "busted sampler" example.  Also, the degree 
of compaction - whatever and however long it persists each season - 
is not enough to prevent strong sward growth.  We are now in the 6th 
grazing year on those swards (different trial now), and growth has 
been outstanding this season, in spite of two, 3-week droughts, one 
in June and the other in August.  Ann





ACLARK@crop.uoguelph.ca
Dr. E. Ann Clark
Associate Professor
Crop Science
University of Guelph
Guelph, ON  N1G 2W1
Phone:  519-824-4120 Ext. 2508
FAX:  519 763-8933